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## Wydział Matematyki, Informatyki i Mechaniki Uniwersytetu Warszawskiego

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# Seminarium „Topologia i teoria mnogości”

5050

## Lista referatów

• 2019-10-09, godz. 16:15, 5050

Mikołaj Krupski (University of Warsaw)

Hereditarily Baire hyperspaces, filters and spaces of measures

A topological space X is Baire if the intersection of a countable family of open dense sets in X is dense. We say that X is hereditarily Baire if every closed subspace of X is Baire. It was observed by the speaker that hereditary Baireness of the hyperspace of all nonempty compact subsets of a s...

• 2019-06-12, godz. 16:15, 5050

Mikołaj Krupski (University of Warsaw)

Embedding of the Free Abelian Topological Group A(X x X) into A(X)

In my talk I will discuss the following question: For which separable metrizable spaces X does the free abelian topological group A(X x X) isomorphically embed into A(X)? While for many natural spaces X such an embedding exist, I will show that there is a compact metric space X (Cook continuum) su...

• 2019-06-05, godz. 16:15, 5050

Piotr Koszmider (IMPAN)

On R-embeddability of almost disjoint families and some problems concerning C*-algebras

An almost disjoint family A of subsets of N is said to be R-embeddable if there is a function f:N→R such that the sets f[A] are ranges of real sequences converging to distinct reals for distinct A∈A. It is well known that almost disjoint families which have few separations, such as Luzin familie...

• 2019-05-29, godz. 16:15, 5050

Tomasz Weiss (Cardinal Wyszyński University in Warsaw)

Some properties of the * operation on families of special subsets of R. Algebraic sum of a perfect set and large subsets of R

In the first part of this talk I will present the following lemma. Assume CH. Given a non trivial ideal F of subsets of R which is Borel supported, translation invariant, with cov(F) =c/the continuum/ and a set A which does not belong to F, there is an X such that for every Y from F , X+Y is not eq...

• 2019-05-22, godz. 16:15, 5050

Tomasz Cieśla (McGill University)

Measurable Hall's theorem for actions of abelian groups

We prove a measurable version of the Hall marriage theorem for actions of finitely generated abelian groups. In particular, it implies that for free measure-preserving actions of such groups, if two equidistributed measurable sets are equidecomposable, then they are equidecomposable usin...

• 2019-05-15, godz. 16:15, 5050

Witold Marciszewski (University of Warsaw)

Twist and Shout - a continuation

We consider the class of Banach spaces Y for which the space c_0 admits a nontrivial twisted sum with Y, i.e., there exists a Banach space X containing a noncomplemented copy Z of c_0 such that the quotient space X/Z is isomorphic to Y. We present a characterization of such spaces Y in terms of prop...

• 2019-05-08, godz. 16:15, 5050

Witold Marciszewski (University of Warsaw)

Twist and Shout

We consider the class of Banach spaces Y for which the space c_0 admits a nontrivial twisted sum with Y, i.e., there exists a Banach space X containing a noncomplemented copy Z of c_0 such that the quotient space X/Z is isomorphic to Y. We present a characterization of such spaces Y in terms of pro...

• 2019-04-17, godz. 16:15, 5050

Damian Sobota (Kurt Gödel Research Center, University of Vienna)

Selected topics in convergence of measures on compact spaces

During my talk I'll present some most recent results of my joint work with Lyubomyr Zdomskyy concerning different aspects of convergence of sequences of Radon measures on compact spaces. Among others, I'll present a (sketch of a) constructive and elementary proof of the fact that the Banach spac...

• 2019-04-10, godz. 16:15, 5050

Rafał Górak (Warsaw University of Technology)

A classification of spaces of continuous functions on ordinals

During my talk, I will present the missing case of the topological classification of spaces of continuous real-valued functions Cp([0, \aplha]) on ordinals. This result was recently presented by Genze, Gulko and Khymyleva (https://arxiv.org/pdf/1806.09015.pdf) and is a continuation of the research I...

• 2019-03-27, godz. 16:15, 5050

Jerzy Kąkol (A. Mickiewicz University)

Grothendieck spaces C(K), Efimov spaces, and the separable quotient problem for spaces C_p(X)

The abstract of the talk can be found here: http://www.mimuw.edu.pl/~wmarcisz/Seminarium/Warszawa-27-03.2019.pdf The next meeting of the seminar is planned on April 10th (there will be no meeting on April 3rd). ...